Question: 8 notebooks cost $14.48. Which equation would help determine the cost of 7 notebooks?
Solution: There are several equations that could help determine the cost, each with a slightly different approach. We know the cost of 8 notebooks. We want to know the cost of 7 notebooks. We can write the numbers of notebooks as a proportion: $\dfrac{8}{7}$ We know 8 notebooks costs $14.48. We can let $x$ represent the unknown cost of 7 notebooks. The proportion of these costs can be expressed as: $\dfrac{\$14.48}{x}$ The cost changes along with the number of notebooks purchased, and so the two proportions are equivalent. $\dfrac{8}{7} = \dfrac{\$14.48}{x}$